Traditionally, vehicles have been provided with antennas mounted in different locations of the vehicle. Usually, these antennas were broadband monopoles located at the rear window and/or on the roof.
FIG. 1a shows a lateral view of a vehicle having a conventional antenna 12 mounted on the roof of the vehicle. FIG. 1b shows a detailed view of the antenna 12 shown in FIG. 1a, where the antenna 12 is fed by a coaxial cable 14 and the roof acts as a ground plane 13.
Over the years, the number of radio-communication services has increased and, in consequence, the number of antennas required for providing these services.
Also, aesthetic and aerodynamic trends have changed and, over the years, satisfying customer tastes has become essential in the automotive industry. Lately, customer tastes generally lead to vehicles having a streamlined and smooth appearance, which interfere with providing the vehicle with multiple and dispersed antennas.
Thus, both for meeting customer tastes and providing all the radio-communication services possibly demanded by the driver, the automotive industry is tending to integrate in a single module all the communication modules specifically designed for providing one communication service, such as telephony, AM/FM radio, satellite digital audio radio services (SDARS), global navigation satellite system (GNSS), or digital audio broadcasting (DAB).
The integration of multiple antenna units in a single global antenna module leads to achieve great advantages in costs, quality and engineering development time.
This global antenna module is subject to meet current customer tastes. For that, it would be desirable to reduce the size of traditional antenna systems in order to be able to integrate them in a module that can maintain the streamlined appearance of the vehicle. However, reducing the size of an antenna system affects its performance.
Further, the automotive industry has to meet customer demands on communication, being thus obliged to provide robust communications in all services available for the driver. For that, it would be desirable to provide an antenna system able to operate in a broad bandwidth with high efficiency.
Then, it would be desirable to develop an improved antenna system for a vehicle that having a reduced size, offers a high efficiency and a broadband behavior. It would be also desirable that the improved antenna system operates on all LTE frequency bands without losing its broadband and high efficient characteristics in any band.